Cal. Government Code § 20750

Subject to regulations adopted by the board, a member may file an election with the board to redeposit in the retirement fund, in a lump sum or by installment payments, (1) an amount equal to the accumulated contributions that he or she has withdrawn at one or more terminations of service, or for one withdrawal at a time, but in reverse chronological order in which they occurred, and (2) an amount equal to the interest that would have been credited to his or her account to the date of completion of payments had the contributions not been withdrawn, and (3) if he or she elects to redeposit in other than one sum, interest on the unpaid balance of the amount payable to the retirement fund, beginning on the date of the election to redeposit, as if the member interest crediting rate in effect on the date of the election to redeposit had been and continued to be in effect through the completion of the payments.